Dung Beetles Duped Into Planting Shrub's Seeds

When it comes to attracting pollinating insects, Cape Restio shrubs have the perfect plan. They produce large, dark nuts that look just like antelope droppings that trick dung beetles into planting them, according to a new study.

"The seeds are very pungent. Humans can easily smell them," Professor Jeremy Midgley, a biologist at the University of Cape Town, told the Daily Mail. "I have nine-month-old seeds in a paper bag in my office that are still very pungent. At this stage only, dung beetles seem to be attracted to the seeds."

Dung beetles feed almost exclusively on animal droppings or "dung," gathering droppings into large balls, rolling them away and burying them to be used for food at a later date or for their larvae to consume. The Cape Restio shrubs use this to their advantage, disguising seeds to look like dung.

(Photo : Jeremy Midgley )Researchers have found that nuts (label a, b and c) gives off strong smelling chemicals that mimic the pungent aroma of antelope droppings (label g). This tricks dung beetles (label f) into rolling them away and ultimately allow the plants to become more widespread.

The seeds from Cape Restio shrubs, also known as Ceratocaryum argenteum, produce chemicals that are 300 times more volatile than those of other seeds from similar plants. As the seeds age, they also become increasingly volatile, according to the study.

To observe the beetles' attraction to the disguised dung, researchers scattered 195 seeds throughout the De Hoop Nature Reserve in South Africa and then used motion-sensing trail cameras and fluorescent markers to track the seeds. Within 24 hours, dung beetles had rolled nearly half of them away.

They also found that some animals favored the seeds for their nutritious nutty interior and wouldn't go near them until they are de-husked, an indication, say researchers, that the smell is repellent. That's definitely an advantage for the shrubs: animals are relleped form eating the seeds, which, in turn, frees them up for beetles to help plant them in widespread locations.

The University of Cape Town study will help researchers identify which volatile chemicals attract beetles and was recently published in the journal Nature Plants.